Cortical bone pin

ABSTRACT

A pin made of cortical bone may be inserted into adjoining bones of a toe to align and secure the bones. The pin may have barbs to prevent migration of the pin. The pin may include a shoulder to further prevent migration of the pin from the bones, to increase the strength of the pin, and to increase the surface area between the bone pin and the host bone. The pin may further include flattened portions on its circumference to aide in rotating the pin during insertion. The pin may be treated to reduce brittleness.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/650,364 filed May 22, 2012, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a pin for use in aligning and securingbones, and more particularly, to such a pin made of cortical bone thatmay be used for aligning and securing bones of a toe of a human patient.The present invention may also be used for aligning and securing bonesof a hand, forefoot, or forearm of a patient. In particular, a fracturedbone of a hand, foot, or forearm may be treated by inserting a pinaccording to the present invention into at least one segment of thefractured bone.

Discussion of the Related Art

Certain deformities such as hammer toe result in the bones of a toebeing arranged in a highly abnormal manner. In some cases, the treatmentfor such deformities involves inserting a K-wire (Kirschner wire)through the tip of the toe and penetrating through the bones of the toeso as to align the bones in a more ordinary manner. According to thisprocedure, the K-wire exits the surface of the skin for a certain periodof time. This method suffers from several drawbacks. First, the K-wireis exposed, allowing for the K-wire to slide out of the toe. Anotherdrawback is the insertion point is an open wound, thus raising thepossibility of infection.

As another treatment, a metal pin may be inserted through an exposedinterphalangeal joint. This method involves the steps of (i) incising atthe appropriate joint, (ii) driving a drill pin into the shaft of theappropriate phalanges, (iii) measuring, with a depth gauge, the depthsof the intramedullary canals, (iv) selecting a pin of an appropriatelength dependent on the measurements of the lengths of theintramedullary canals, (v) inserting the pin into the proximal phalange,and (vi) placing the distal phalange over the pin. This method suffersfrom the several drawbacks. First, the metal pin is not resorbable noris it removable. Another drawback is the pin may migrate into one of thephalanges (especially the proximal phalange). This may cause instabilityand a failure to fuse. In extreme cases, one of the phalanges(especially the distal phalange) may become detached from the pin.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a pin thatsubstantially obviates one or more of the problems in the prior art.

In one aspect of the invention, a pm has an elongated body of asubstantially cylindrical shape. The pin may include a raised portion,or a plurality of raised portions, that may be formed of peaks andtroughs. Such raised portions are referred to herein as “barb(s).” Thebarbs may extend around the entire circumference of the pin. In certainembodiments, however, the barbs are located on only a portion of thecircumference of the pin. The remainder of the circumference of the pinmay be flattened. In certain embodiments, voids are created along thecircumference of the barbs to create spokes. The pin may include aprotrusion (also referred to as a “shoulder”) extending outward from thepin. In some embodiments, the pin is made of cortical bone. In someembodiments, the cortical bone pin is treated to reduce brittleness.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a perspective view of a pin according to a first exemplaryembodiment of the present invention.

FIG. 2 is a top view of a pin according to a first exemplary embodimentof the present invention.

FIG. 3 is a side view of a distal portion of a pin according to a firstexemplary embodiment of the present invention.

FIG. 4 is a side view of a proximal end of a pin according to a firstexemplary embodiment of the present invention.

FIG. 5 shows a pin according to a first exemplary embodiment of thepresent invention partially inserted into the toe of a patient.

FIG. 6 shows a pin according to a first exemplary embodiment of thepresent invention fully inserted into the toe of a patient.

FIG. 7 is a top view of a double-ended drill used to drill out theintermedullary canals of the bones into which a pin according to thepresent invention is to be inserted.

FIG. 8 is an end view of a double-ended drill used to drill out theintermedullary canals of the bones into which a pin according to thepresent invention is to be inserted.

FIG. 9 is a perspective view of a pin according to a second exemplaryembodiment of the present invention.

FIG. 10 is a top view of a pin according to a second exemplaryembodiment of the present invention.

FIG. 11 is a detailed view of a barb of a pin according to a secondexemplary embodiment of the present invention.

FIG. 12 is a perspective view of a pin according to a third exemplaryembodiment of the present invention.

FIG. 13 is an end view of a pin according to a third exemplaryembodiment of the present invention.

FIG. 14 is a perspective view of a pin according to a fourth exemplaryembodiment of the present invention.

FIG. 15 is an end view of a pin according to a fourth exemplaryembodiment of the present invention.

FIG. 16 is a top view of a pin according to a fifth exemplary embodimentof the present invention.

FIG. 17 is a view of a pin according to a fifth exemplary embodiment ofthe present invention taken along section line 17-17 in FIG. 16.

FIG. 18 is a perspective view of a pin according to a fifth exemplaryembodiment of the present invention and an insertion tool used to inserta pin according to a fifth exemplary embodiment of the present inventioninto the bones of a patient.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIGS. 1-4 show a pin 1 according to a first exemplary embodiment of thepresent invention. As shown in FIG. 1, the pin 1 has a substantiallycylindrical shape.

As shown in FIGS. 1-2, in one embodiment, barbs 2 are provided on thedistal end of the pin. Barbs are preferred over threads as the torquerequired to install a threaded pin may stress the pin to failure. Asshown in FIG. 3, the profile of the barbs 2 may be such that, as a barb2 proceeds from a distal end to a proximal end, the barb 2 slopesgradually from a trough 5 to a crest 6, with an abrupt slope from acrest 6 to a trough 5. This way, the barbs 2 are designed to resistmigration of the pin 1 toward a proximal direction after the pin hasbeen inserted into the bone of a toe of a patient. Similarly, the barbs2 are designed to resist migration of a distal bone of a patient fromthe pin 1. The barbs 2 may extend completely around the circumference ofthe pin 1 according to the invention.

As shown in FIGS. 1-2, in one embodiment, a shoulder 4 is provided. Thisshoulder 4 may have a diameter greater than the remainder of the pin 1.For example, the shoulder 4 may have a diameter that is approximately110%, 115%, 120%, 130%, 150%, 170%, 200%, 250%, 300% or 400% of thediameter of the remainder of the pin 1. The diameter of the remainder ofthe pin 1 may be approximately 1 mm, 2 mm, 3 mm, or 4 mm. The shoulder 4may have sloped surfaces 9 and 10 on either side of the apex of theshoulder 4 as depicted in FIGS. 1 and 2. According to the invention,surfaces 9 and 10 may also be contoured, convex, concave, stepped, orirregular to complement the surface area created inside the bone. Forexample, the internal surface area of the bone may be created and/orshaped by the drilling of the intramedullary canals using a drill bithaving various profiles. FIGS. 1, 2 and 7 show a sloped profile; ofcourse, drill bits and shoulder surfaces having other profiles may beemployed in other embodiments. In some aspects, pins are designed suchthat the surface(s) of the pin are complementary to the internal surfacearea of the bone to maximize, to the extent possible, surface proximityand fusion efficiency. Additionally, the shoulder 4 is designed toprevent migration of the pin 1 into a proximal bone. Thus, it is notnecessary that the length of the pin equal the combined lengths of theintramedullary canals of the phalanges. By contrast, in the prior artpractice, the length of the pin must be very nearly equal to thecombined lengths of the intramedullary canals of the phalanges. In thesesystems, incorrect selection of the length of the pin may result in pinmigration, resulting in instability and failure to fuse. Further, inthis application the bone pin undergoes relatively large stress at theproximal bone-bone pin interface. However, according to the invention,because the shoulder 4 has a relatively large diameter, the pin 1 iswell suited to undergo the stresses at the proximal bone-bone pininterface. Additionally, as mentioned above, in one embodiment thesloped surfaces 9 and 10 of shoulder 4 increase the surface area ofcontact between the pin 1 and the host bone, which tends to promotefusion. It being understood that other shoulder profiles may provideimproved surface area proximity and fusion efficiency in the case wheredrill bits having other profiles are employed for example.

In one embodiment, barbs 3 are provided on the proximal end of the pin1. As shown in FIG. 4, these barbs 3 are similar to barbs 2; however,barbs 3 may have a profile such that, as the barb 3 proceeds from adistal end to a proximal end, the barb 3 slopes abruptly from a trough 7to a crest 8 and slopes gradually from a crest 8 to a trough 7. Thisway, the barbs 3 are designed to resist migration of the pin 1 toward adistal direction. The barbs 3 may extend completely around thecircumference of the pin 1 according to the invention.

In one aspect, the diameters of the features of the proximal portion ofthe pin may be slightly larger than the diameters of the correspondingfeatures of the distal portion of the pin. In other words, the diameterof crest 8 may be slightly larger than the diameter of crest 6, and thediameter of trough 7 may be slightly larger than the diameter of trough5.

The pins of the invention may be made from cortical bone. The corticalbone may be human cortical bone or animal cortical bone. It isunderstood that pins and bone pins are used interchangeably throughoutthe description and that a pin made of cortical bone is one preferredmaterial of construction for the pin. In addition to cortical bone,other resorbable and biocompatible materials may be used. Additionally,non-metallic synthetics may be used for the pin material. Cortical bone,resorbable and biocompatible materials, and non-metallic synthetics arepreferred pin materials compared to metals to promote enhanced fusion.

As described in further detail below, a bone pin according to thepresent invention may be made and treated according to the followingprocedures.

In certain embodiments, the bone pin is cleaned according to the methodsdescribed in U.S. Pat. Nos. 5,556,379; 5,797,871; 5,820,581; 5,976,104;5,977,034; and 6,024,735.

The bone pin may be machined by a CNC machine. Alternatively, othermanufacturing methods may be used.

In another embodiment, after the bone pin has been cleaned anddisinfected, it may be demineralized in accordance with the disclosuresof U.S. Pat. Nos. 6,534,095; 6,830,763; 6,189,537; and 6,305,379, all ofwhich are hereby incorporated by reference. This reduces or eliminatesthe likelihood of disease transmission and/or improves fusion. Thedemineralization may be a surface demineralization. The surfacedemineralization may be applied to the whole body or a portion of thebone pin 1, such as the shoulder 4. In some embodiments, thedemineralized portion of the bone tissue is at least 10%, 20%, 30%, 40%,50%, 60%, 70%, 80%, or 90% (v/v %) of the bone tissue. In otherembodiments, the demineralized portion of the bone tissue is less than10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% (v/v %) of the bonetissue. This may be accomplished by covering the portions of the bonepin not to be demineralized with acid resistant materials, such asparaffin, with the areas to be demineralized, such as shoulder 4, leftexposed. For example, the portions of the bone pin I labeled “A” in FIG.2 may be covered with a paraffin, while the portion of the bone pin Ilabeled “B” in FIG. 2 may be exposed. The bone pin may then be treatedwith an acid solution for a desired amount of time. The acid-resistantmaterial, such as paraffin, may then be removed. In one aspect, this maybe accomplished by first refrigerating the bone pin and then detachingthe paraffin shell from the bone pin. The absorbed acid may then beremoved by rinsing. The depth of demineralization can be controlled byadjusting the type and concentration of the acid solution, and/or theexposure time of the bone pin to the acid solution. The demineralizationmay also be a full demineralization of a portion of the bone pin, suchas the shoulder 4, to enhance bone incorporation and/or create astructural zone with more flexibility.

The above-described “partial demineralization” technique can be appliedto other types of cortical or cortical-cancellous bone grafts to controlthe exact area and depth of demineralization. For example, a cranialbone flap can be processed through such method to be osteoinductive thuspromoting new bone formation and fusion to the adjacent host bone, whilestill maintaining certain mechanical integrity. The treated graft isthus able to withstand surgical fixation through metal plates andscrews. The exterior (i.e. abaxial) surface of the cranial bone flap,facing the outside of a body, can be first covered with acid resistantmaterials such as paraffin. The cranial bone flap may then be treatedwith acid solution to demineralize the interior (i.e. adaxial) surfaceof the cranial bone flap, facing the cranial cavity. Of course, as isreadily understood by those skilled in the art, acid resistant materialsmay be employed in various patterns and arrangements in order todemineralize certain portions and leave others untreated as desired.

In another embodiment, the bone pin may be treated in accordance withthe disclosures in U.S. Pat. Nos. 6,293,970, 6,544,289, and 7,063,726,all of which are hereby incorporated by reference, which act to improvethe preservation of the bone pin. In particular, the followingadvantages over conventional methods of preservation may be realized.One conventional method of preservation is freezing the bone graft witha liquid. This requires keeping the bone graft in a very cold (such as−80° F.) environment, which may be difficult and expensive. Anotherconventional method of preservation is freeze-drying the bone graft.However this method results in a brittle bone graft. Further, thesurgeon must rehydrate the bone graft prior to insertion into a patient.By contrast, by treating the bone pin in accordance with the disclosuresin U.S. Pat. Nos. 6,293,970, 6,544,289, and 7,063,726, the bone pin maybe stored at room temperature, the bone pin is not brittle, and asurgeon need only briefly rinse the bone pin prior to insertion into apatient.

An exemplary method of inserting the above-described cortical bone pininto a patient is described with reference to FIGS. 5-8. The methoddescribed below is similar to the method described by Dr. Stephen J.Miller in Hammer Toe Correction by Arthrodesis of the ProximalInterphalangeal Joint Using a Cortical Bone Allograft Pin, Journal ofthe American Podiatric Medical Association, Vol. 92, No. 10, pp. 563-69(2002). First, as with the method described by Dr. Miller, an incisionis made above the appropriate joint. The subcutaneous layer isseparated. The extensor tendons are retracted or separated, thecollateral ligaments are incised, and the joint is brought to theincision. The cartilage from the joint surfaces is then removed. Theintramedullary canals of the proximal and distal bones are drilled. Adouble-ended drill, such as that shown in FIGS. 7-8 (described below),may be used for this step. Migration of the bone pin 1 of the presentinvention into the proximal phalange is prevented by the shoulder 4.Accordingly, unlike the method described by Dr. Miller, although thesurgeon may measure the depths of the intramedullary canals when using abone pin according to the present invention, it is not necessary to doso. Further, although a surgeon may do so, it is not necessary to cut apin to the length of the combined measured depths. According to oneaspect of the invention, the bone pin 1 may be inserted into theproximal phalange with the shoulder 4 abutting the end of the phalangeas shown in FIG. 5. The distal phalange may then be brought up over thebone pin 1 and may be inserted onto the bone pin 1, as shown in FIG. 6.The incision is then closed.

The double-ended drill referenced in the process above will now bedescribed with reference to FIGS. 7-8. The double-ended drill 170 mayinclude a distal side 173 and a proximal side 175 separated by a hiltstop 178, which may be locatedat the center of the double-ended drill170. The drill may include a distal drill 172 and proximal drill 174 andhilt stops 176 and 177. The drill may further include hex flats 182. Thedrill may also include a detent ball 183 on each side of the drill. Thehilt stop 178, hex flats 182 and detent balls 183 may be used inaccommodating the drill in standard drill chucks. The overall length 171of the drill may be from about 3 inches to about 6 inches. The distaldrill 172 and proximal drill 174 may include at least one flute (notshown) along their main shafts and auto-centering drill points. Thelength of the proximal drill 174 may be about 35 mm or less on a drillhaving an overall length of 3 inches. The length of the distal drill 172may be approximately one-half the length of the proximal drill 174. Theoverall lengths of the distal side 173 may be equal to the overalllength of the proximal side 175, and these lengths may be independent ofthe lengths of the distal drill 172 and proximal drill 174. The width ofhex flats 182 may be about ¼ inch, ⅜ inch or ½ inch. The face of hiltstops 176 and 177 may be approximately 60° and may include at least oneflute (not shown) for cutting a chamber at the insertion point.

In addition to the treatment of hammer toe, the present invention issuitable for other applications, such as the treatment of a fracturedbone in a hand, foot, or forearm. In particular, the segments of thefractured bone may be aligned and secured by a cortical bone pindescribed herein.

A second exemplary embodiment of the present invention will now bedescribed with reference to FIGS. 9-11. As shown in FIG. 9, a pinaccording to a second embodiment includes barbs 101 and a hilt 102.

As depicted in FIG. 10, the pin includes a proximal barb section 111 anda distal barb section 113 separated by the hilt 102. The proximal barbsection 111 may be twice the length of the distal barb section 113. Thewidth of the hilt 102 (indicated by 112 in FIG. 10) may be about 0.0 mmto about 5.0 mm. Each barb may have a barb angle 114, being symmetricalto the center line of the pin, of for example approximately 15° toapproximately 25°.

Details of the barbs will now be described with reference to FIG. 11. Abarb crest 121 may be pointed or dull. A frustum connection 122 whichconnects each barb with an adjacent barb may be sharp or rounded. A barbminor diameter 123 may be approximately 65% to approximately 75% of abarb major diameter 124, and the barb major diameter 124 may beapproximately 130% to approximately 150% of the barb minor diameter 123.Half of the difference between the barb major diameter 124 and the barbminor diameter 123 yields the barb height 126. A barb frustum angle 127may be obtuse, creating a dull crest, or acute, yielding a sharp andpointed crest. The barb length 125 may be approximately 1.0 mm toapproximately mm and may vary from barb to barb on the same pin.

A third exemplary embodiment of the present invention will now bedescribed with reference to FIGS. 12-13. In the first and secondexemplary embodiments, the barbs are depicted as being frustoconical.The outer surface of each barb is continuous and each cross sectiontaken perpendicular to the main axis of the pin may be defined by acircle. In the third exemplary embodiment, by contrast, various voidsare created in each barb, resulting in spokes 131.

A fourth exemplary embodiment of the present invention will now bedescribed with reference to FIGS. 14-15. Similar to the third exemplaryembodiment, various voids may be created in each barb, resulting inspokes 151.

A fifth exemplary embodiment of the present invention will now bedescribed with reference to FIGS. 16-18. Because the bone pin 11according to this embodiment is similar to the bone pin 1 according tothe first exemplary embodiment, only the differences between bone pin 1and bone pin 11 will be described. Whereas bone pin 1 is depicted ashaving a substantially circular cross section across its length, bonepin 11 includes flattened side surfaces 13 as shown in FIGS. 16 and 17.These flattened side surfaces 13 may be located on opposite sides of thedistal end of bone pin 11. These flattened side surfaces 13 allow forthe use of a tool 20, shown in FIG. 18, during insertion of the bone pin11 into the proximal phalange. In one embodiment, the tool 20 issubstantially cylindrical and substantially hollow. Flattened surfaces21 may be formed on the inside of the tool and may be designed to engagewith the flattened side surfaces 13 of the bone pin 11. According to oneaspect, when the tool 20 is rotated, the bone pin 11 rotates duringinsertion into the proximal phalange.

Other than the specific differences noted above, the second throughfifth exemplary embodiments may be similar to the first exemplaryembodiment. Thus, for example, the pins according to the second throughfifth exemplary embodiments may be made of the same material as thefirst exemplary embodiment, and may be cleaned, demineralized, andtreated according to the same procedures described with reference to thefirst exemplary embodiment.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the pin of the presentinvention without departing from the spirit or scope of the invention.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents.

1.-24. (canceled)
 25. A method for using a bone pin, having an elongatedbody, to align and secure a bone, the method comprising: creating anincision in at least one bone segment of a foot, forearm or hand;drilling an intramedulliary canal between proximate and distal ends ofthe at least bone segment; inserting the bone pin into theintramedulliary canal, wherein the bone pin comprises: a proximalportion; a distal portion; barbs on the proximal portion; barbs on thedistal portion, wherein the barbs on the proximal portion have a profilesuch that, as the barbs proceed from a distal end to a proximal end ofthe bone pin, the barbs slope abruptly from a trough to a crest andslope gradually from a crest to a trough, and wherein the barbs on thedistal portion have a profile such that, as the as the barbs proceedfrom a distal end to a proximal end of the bone pin, the barbs slopegradually from a trough to a crest and slope abruptly from a crest to atrough; and a shoulder between the proximal portion and the distalportion, wherein the shoulder has an apex and sloped, contoured, convex,concave, stepped, or irregular surfaces extending gradually on eitherside of the apex of the shoulder.
 26. The method of claim 25, whereinthe bone pin is inserted into the intramedulliary canal of a proximalphalange of a patient to treat hammer toe.
 27. The method of claim 25,wherein the bone pin is inserted into the intramedulliary canal of ajoint of a fractured bone or deformed bone or joint of the hand, foot orforearm.
 28. The method of claim 25, wherein the bone pin furthercomprises flattened surfaces on opposite sides of the bone pin.
 29. Themethod of claim 28, wherein the flattened surface are disposed on thedistal portion of the bone pin.
 30. The method of claim 25, wherein thebone pin comprises cortical bone.
 31. The method of claim 30, whereinthe cortical bone is human cortical bone.
 32. The method of claim 30,wherein the cortical bone is animal cortical bone.
 33. The method ofclaim 25, wherein the bone pin comprises resorbable materials.
 34. Themethod of claim 25, wherein the bone pin comprises non-metallicsynthetic materials.
 35. A method for using a bone pin, having anelongated body, to align and secure a bone, the method comprising:creating an incision in at least one bone segment of a foot, forearm orhand; drilling an intramedulliary canal between proximate and distalends of the at least bone segment; inserting the bone pin into theintramedulliary canal, wherein the bone pin comprises: a proximalportion; a distal portion; and a shoulder between the proximal portionand the distal portion, wherein the should has a diameter greater than aremainder of the bone pin, and wherein the shoulder has an apex andsloped, contoured, convex, concave, stepped, or irregular surfacesextending gradually on either side of the apex of the shoulder.
 36. Themethod of claim 35, wherein the bone pin is inserted into theintramedulliary canal of a proximal phalange of a patient to treathammer toe.
 37. The method of claim 35, wherein the bone pine isinserted into the intrmedulliary canal of a joint of a fractured bone ordeformed bone or joint of the hand, foot, or forearm.
 38. The method ofclaim 35, further comprising barbs on the proximal portion of the bonepin; and barbs on the distal portion, wherein the barbs on the proximalportion have a profile such that, as the barbs proceed from a distal endto a proximal end, the barbs slope abruptly from a trough to a crest andslope gradually from a crest to a trough, and the barbs on the distalportion have a profile such that, as the barbs proceed from a distal endto a proximal end, the barbs slope gradually from a trough to a crestand slope abruptly from a crest to a trough.
 39. The method of claim 38,wherein the bone pin further comprises flattened surface on oppositesides of the bone pin.
 40. The method of claim 39, wherein the flattenedsurfaces are disposed on the distal portion of the bone pin.
 41. Themethod of claim 35, wherein the bone pin comprises cortical bone. 42.The method of claim 41, wherein the cortical bone is human corticalbone.
 43. The method of claim 41, wherein the cortical bone is animalcortical bone.
 44. The method of claim 35, wherein the bone pincomprises resorbable materials.
 45. The method of claim 35, wherein thebone pin comprises non-metallic, synthetic materials.